#include"stdio.h"
main()
{
    int a[50],i = 0,sum = 0;
float ave;
scanf("%d",&a[i]);
while(a[i] != -1)
   { 
    sum += a[i];
    i++;
scanf("%d", &a[i]);
} 
ave = (float)sum / i;
printf("average=%f\n ",ave);
return 0;
}